Digital communications methods are methods that send digital information (encoded in bits, 0 or 1) instead of sending an analog signal, such as voice or video.
The methods listed here are all digital modes:
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APRS, Automatic Packet Reporting System, is a standard utilizing packet radio and a GPS to send beacons with the location of the unit. There are many things you can do with APRS, but many use it on bicycles to track their progress, on their vehicle to track where it is, etc. There have even been reports of APRS- equipped vehicles being stolen and then quickly tracked down thanks to the APRS unit.
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Automatic location reports need to know the location to automatically report; thus, they use a GPS just like anything else would =]
If you think about this one, it couldn't be the speedometer anyway; that would only tell you how fast you are going. (also APRS, Automatic Position Reporting System, can be used when biking, driving, walking, etc all just as easily as the other). The other two options are just random things thrown in hoping you won't know what they are so you'll guess wrong. Nearly everyone knows what a GPS is, so this shouldn't be hard to remember.
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If you ask a broadcast engineer, NTSC stands for Never The Same Color, because her job is to keep all the cameras looking the same. Now that TV is in the Digital Age the only people you see using the NTSC broadcast standard are Amateur Radio Operators.
Actually, NTSC stands for National Television Systems Committee. They created the rules that governed what the broadcast signal would be electronically so every TV would be able to display the correct picture. And what all this has to do with analog fast scan color TV signals, no one really knows.
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It helps to know what APRS is and does. It transmits a station's GPS coordinates, so other stations can locate it. The components are a GPS receiver, a ham radio transmitter, and some logic to connect the two so the transmitter sends out the GPS coordinates. So:
It has nothing to do with counting packets, It doesn't require voice over Internet, and It doesn't count stations connected to a repeater.
It just provides real time communications that gives your location. In conjunction with a map, it shows your location to the stations that receive your GPS coordinates via the APRS system.
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A checksum is an error detection method used by many data transmission types including packet radio. Basically all bytes in the message are added (summed) up and sent as a "checksum". The receiving station repeates this process and "checks" the result against the checksum it received from the sending station.
If the checksum fails (the sums don't match) then an automatic repeat request is sent.
Since packet radio is a form of amateur radio communications the destination station is generally identified at least by call sign, so that information is often included in the header as well.
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CW stands for "Continuous Wave", which is a sine wave: an electromagnetic wave of constant amplitude and frequency.
This wave can be interrupted, creating an "off" state. The on and off states can be used to transmit Morse code.
The original version of Morse code developed by Samuel Morse is often referred to as Railroad Morse code or American Morse code—American because the rest of the world adopted International Morse. Eventually International Morse also replaced Railroad Morse in America, and this is what we use today.
The term CW comes up a lot; whether you remember what CW stands for or not, every amateur radio operator should know that CW means Morse code.
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ARQ stands for Automatic Repeat reQuest
When the receiving station detects an error, it automatically sends a repeat request to the sending station.
It has nothing to do with encryption (which would be illegal except for sending commands to a satellite), or video signals, or data compression. Indeed, it takes a long time to have the receiving station send a repeat request and to then re-transmit the message, or portion of the message.
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Broadband-Hamnet™ was at one time called HSMM-Mesh™ and is one of a couple of different projects which are basically intended to create a peer to peer wireless network on ham radio frequencies.
The first iteration of this involved using the Linksys WRT-54G -- a highly modifiable consumer access point -- with custom firmware on 2.4ghz channel 1, which is actually part of the ham radio allotted spectrum. The idea is that "mesh nodes" can connect to each other automatically and route traffic between each other, thus providing a wireless network which covers a city (or larger) by creating interlinking nodes.
In practice this is more difficult than you might expect, due to congestion on 2.4ghz frequencies, but the project has expanded to include support for other access points and bands as well. There are some offshoots of the project, including AREDN (Amateur Radio Emergency Data Network) and HamWan.
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An electronic keyer is the modern fancy replacement for the traditional telegraph key, or in other words a device that assists in manual sending of Morse code.
Electronic keyers can have a variety of functions including:
Often they are hardware devices but they can also be computer or smartphone software applications that provide these and other functions.
Electronic keyers.... They just might save you from carpel-tunnel syndrome!
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